A recessed reflector-type downlight described in German patent document 1,262,182 of E. Price and I. Goodbar of the socalled dark light type is designed based on the concept that the light source is an array of point sources. The curvature of the reflector is set such that the light is cast in a strictly defined space shaped, when the reflector is symmetrical to a vertical line, as a cone and, when the reflector is elongated with two sides symmetrical to a vertical plane, as a downwardly flaring triangular-section band. With appropriate shaping of one side of the reflector, the system can be used for casting most of its light laterally for wall-washing effect.
In such a system the shape of the reflector, determined by a complex calculation, is such that light emitted by the surface of the light source is reflected by the reflector surface formed on the inside of the reflector outward in a space symmetrical to a symmetry plane of the reflector and defined by a family of lines tangenting an edge of the reflector and traversing the symmetry plane at a common point or line. The result is areas to either side of the fixture that get no light directly off the light source or reflector surface. For this to happen the light source has to be confined to a predetermined space within the rear end of the reflector, that is with its light-emitting surface in a predetermined position relative to the reflector surface, as otherwise the beam cast by the reflector will not have the desired shape. Ideally the light-emitting surface must lie on the above-mentioned family of lines that cross at the symmetry plane and tangent the reflector edge, but above the point or line where they cross. If the light source projects downward past this imaginary region, the light will not illuminate as desired and as required by a high-quality down-light.
When such a fixture is used with a high- or low-voltage halogen lamp or with a particularly small-format incandescent or fluorescent bulb, in particular in a wall-washing application as described in German patent document 2,336,418 of E. Price, it is impossible to achieve the desired effect. Such lamps often have irregular surfaces that cannot be used with an accurately shaped reflector.